Can't change a program from read only

I have never had problems with XP until I bought a PC (HP) which came pre loaded with XP. I ran it before but it was a comp that I built. I think due to the settings that HP has in place I am having trouble changing a file for a program that I installed so that it is not read only. I have half a clue about it but not enough to go into things and make changes. The tech rep from the software co said that I need to load safe mode to make the changes that need to be made. If anyone can help it would be appreciated.